From the desk of: Sergey A. Krupenko, Ph.D.
Life expectancy keeps growing in developed countries, approaching 90 years on average in some. There is a forecast that more than 50 percent of girls born in the U.S. after 2010 will live to become 100 years or even older, and that the first person to live up to 150 years has already been born. Perhaps most people are curious about which factors define that people live longer. Obviously, genetic background plays a significant role in a person’s natural longevity. What about diet? Can nutrients help to prolong our life? One of the principal dietary factors influencing our overall health status is calorie consumption. Intuitively, limiting calories to some extent would be expected to improve health conditions and, as such, seems promising for longer life. Indeed, there is a common belief in modern society that skinny people are healthier than obese people. But, does it mean they will live longer? Numerous research papers beginning in the late 1990s and early 2000s indicate that calorie restriction extends lifespan in a wide spectrum of organisms. However, a paper published last year indicates that the issue regarding the influence of calorie restriction on lifespan might not be so simple.
In this study, an international research team led by scientists from the University of Sydney used 25 diets differing in protein, carbohydrate, fat content and energy density to feed mice. The team aimed to correlate macronutrient intakes to longevity, in particular testing the extent to which lifespan in ad libitum-fed (unlimited food) mice is determined by calorie intake per se or by the balance of protein to carbohydrate. With no surprise, this study showed a very complex interplay between dietary protein, carbohydrates, total energy intake and lifespan. Using a very sophisticated mathematical approach, researchers were able to untangle these complex data. They found that lifespan was greatest for animals whose foods were low in protein and high in carbohydrate, and it was not influenced by total calorie intake. This study also identified the molecular target, which is likely responsible for translating the dietary ratio of proteins and carbohydrates to lifespan. A protein kinase mTOR (stands for mammalian target of rapamycin), which regulates several key cellular processes, was activated as dietary ratio between proteins and carbohydrates was shifted towards the former. Since the activation of mTOR is pro-aging, this would explain the life-extending effects of a low-protein, high-carbohydrate diet.
IMPLICATIONS OF THIS STUDY FINDINGS
While it still needs to be confirmed that findings of this study are applicable to humans, they are in line with epidemiological studies showing that low-protein, high-carbohydrate diets are associated with improved health in humans. Accordingly, high-protein diets, widely promoted for weight loss and health, should be taken with precautions. Overall though, rather than specific macronutrients themselves, it is their interactive effects (i.e., balanced diet) that are more important for health and aging.
TAKE-HOME MESSAGE
Excitingly, because mTOR can be targeted by drugs, this also opens a window of opportunity to pharmacological life extension in the future. However, while such an opportunity might be on the horizon, it is still a good idea to limit calorie consumption and engage in regular physical exercises.
Reference: The Ratio of Macronutrients, Not Caloric Intake, Dictates Cardiometabolic Health, Aging, and Longevity in Ad Libitum-Fed Mice (Cell Metab. 2014 Mar 4;19(3):418-30)
